如何用C++实现常见的排序算法（如冒泡排序、快速排序、归并排序等）？

在C++中实现常见的排序算法，比如冒泡排序、快速排序和归并排序，可以按照以下步骤：

1. **冒泡排序**:

   void bubbleSort(int arr[], int n) {
       for (int i = 0; i < n - 1; i++) {
           for (int j = 0; j < n - i - 1; j++) {
               if (arr[j] > arr[j + 1]) {
                   swap(arr[j], arr[j + 1]);
               }
           }
       }
   }

2. **快速排序**:

   void quickSort(int arr[], int low, int high) {
       if (low < high) {
           int pi = partition(arr, low, high);
           quickSort(arr, low, pi - 1);
           quickSort(arr, pi + 1, high);
       }
   }

   int partition(int arr[], int low, int high) {
       int pivot = arr[high];
       int i = (low - 1);
       for (int j = low; j <= high - 1; j++) {
           if (arr[j] < pivot) {
               i++;
               swap(arr[i], arr[j]);
           }
       }
       swap(arr[i + 1], arr[high]);
       return (i + 1);
   }

3. **归并排序**:

   void merge(int arr[], int l, int m, int r) {
       int n1 = m - l + 1;
       int n2 = r - m;

       int L[n1], R[n2];

       for (int i = 0; i < n1; i++)
           L[i] = arr[l + i];
       for (int j = 0; j < n2; j++)
           R[j] = arr[m + 1+ j];

       int i = 0, j = 0, k = l;

       while (i < n1 && j < n2) {
           if (L[i] <= R[j]) {
               arr[k] = L[i];
               i++;
           } else {
               arr[k] = R[j];
               j++;
           }
           k++;
       }

       while (i < n1) {
           arr[k] = L[i];
           i++;
           k++;
       }

       while (j < n2) {
           arr[k] = R[j];
           j++;
           k++;
       }
   }

   void mergeSort(int arr[], int l, int r) {
       if (l < r) {
           int m = l+(r-l)/2;
           mergeSort(arr, l, m);
           mergeSort(arr, m+1, r);
           merge(arr, l, m, r);
       }
   }